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An Ex Post Facto Evaluation Framework for Place-Based Police Interventions

NCJ Number
Evaluation Review Volume: 35 Issue: 6 Dated: 2012 Pages: 592-626
Date Published
35 pages

This report presents the research methodology and outcomes of an assessment of the effectiveness of the Boston Police Department’s safe Street Team, hot spots policing program.


A small but growing body of research evidence suggests that place-based police interventions generate significant crime control gains, although while those policing strategies have been adopted by a majority of U.S. police departments, very few agencies make a priori commitments to rigorous evaluations. Recent methodological developments were applied to conduct a rigorous ex post facto evaluation of the Boston Police Department’s Safe Street Team (SST) hot spots policing program. The research design was a nonrandomized quasi-experimental design, used to evaluate the violent crime control benefits of the SST program at treated street segments and intersections relative to untreated street segments and intersections. Propensity score matching techniques were used to identify comparison places in Boston. Growth curve regression models were used to analyze violent crime trends at treatment places relative to control places. Units of Analysis: Using computerized mapping and database software, a micro-level place database of violent index crimes at all street segments and intersections in Boston was created. The key outcome measurement was yearly counts of violent index crimes that were taken between 2000 and 2009 at the treatment and comparison street segments and intersections. Results showed that the SST program was associated with a statistically significant reduction in violent index crimes at the treatment places relative to the comparison places without displacing crime into proximate areas. To overcome the challenges of evaluation in real-world settings, the authors suggest that evaluators need to continuously develop innovative approaches that take advantage of new theoretical and methodological approaches. Publisher Abstract Provided

Date Published: January 1, 2012